The present invention relates to control systems for model trains, and in particular to Lionel trains with an "E-Unit" electrical motor direction reversing unit.
Model train systems have been in existence for many years. In the typical system, the model train engine is an electrical engine which receives power from a voltage which is applied to the tracks and picked up by the train motor. A transformer is used to apply the power to the tracks. The transformer controls both the amplitude and polarity of the voltage, thereby controlling the speed and direction of the train. In HO systems, the voltage is a DC voltage. In Lionel systems, the voltage is an AC voltage, the 60 Hz line voltage available in a standard wall socket.
In addition to controlling the direction and speed of a train, model train enthusiasts have a desire to control other features of the train, such as a whistle. Lionel allows for such control of the whistle by imposing a DC voltage on top of the AC line voltage, which is then picked up by the locomotive. Obviously, this method is limited in the number of controls that can be transmitted, since there are only plus and minus DC levels available, along with varying amplitudes. One method for increasing the number of control signals available by use of a state machine in the locomotive is disclosed in Severson, U.S. Pat. No. 4,914,431.
Another type of control system is shown in Hanschke et al., U.S. Pat. No. 4,572,996. This patent teaches sending address and control signals over a rail line bus to a train. The signals sent appear to be digital pulses. In Kacerek, U.S. Pat. No. 3,964,701, each train locomotive will respond to a different frequency signal. After the corresponding frequency signal is sent to alert the train, it is followed by a voltage level indicating the action to be taken.
Originally, Lionel trains used a mechanical lever on the locomotive to reverse the direction of the train. The introduction of the E-Unit allowed remote control of the direction of the train. The E-Unit is mounted on the locomotive and has a solenoid coil which is provided power from the train track. When power is removed momentarily, the solenoid coil relaxes and the plunger from the solenoid dislodges a pawl (pivoting arm) away from a ratchet tooth of a drum. When the solenoid is reactivated by reapplying power, the plunger is withdrawn upward, whereby the pawl catches a tooth on the drum, thereby rotating to the next state. The drum has contacts on it which connect with spring contacts from the track power and the motor. The contacts switch as the drum is rotated to interchange the connections of the motor armature with respect to the motor field. The rotating drum will sequence the motor through forward, neutral before reverse, reverse, and neutral before forward.
One disadvantage of the E-Unit is the very nature of its control by removing power. Power can be removed unintentionally by unwanted power interruptions such as a dirty track or loose connections. This can cause the E-Unit to change its state when it should not. In addition, the nature of the E-Unit requires that the solenoid be on all the time that the motor is in a particular position. This results in a continuous buzz emitted by the E-Unit during operation and a significant power drain. This audible buzz is due to the applied AC field mechanically vibrating the plunger and increases with the applied voltage.
One solution to the E-Unit problems is to substitute a new control system with a modified E-Unit. The new control system can operate by sending control signals to the locomotive, rather than by interrupting power on the train track. However, a disadvantage of this system is that a new train equipped for operating in such a control system will not operate when placed on an older train track system which provides control by momentarily removing power. Thus, one could not take one's locomotives to a friend's track system and be assured of compatibility.